A light emitting diode lighting device including a non-insulated step-down chopper is conventionally known. In the conventional light emitting diode lighting device including the non-insulated step-down chopper, a resistance element having a small resistance value is connected between an FET, which is a first switching element and a first inductor, and connected between a base and an emitter of a bipolar transistor which is a second switching element. A collector of the transistor is connected to a gate terminal of the FET. The first inductor and a freewheel diode are connected in series to each other between output terminals.
When the FET is turned on, an increased current flows from a DC source via the resistance element, the first inductor and a capacitor connected in parallel to an LED circuit as a load so that the first inductor is charged. When voltage between both ends of the resistance element then reaches bias voltage for operating the transistor, the transistor is turned on and thus the FET is turned off. Since the voltage between both the ends of the resistance element is set as a base bias voltage and the transistor is turned on and the FET is turned off when the voltage reaches a predetermined voltage, timing of turn-off can always be exactly taken regardless of the voltage value induced in a second inductor. That is, the FET can always be exactly switched on/off.
When the FET is turned off, electromagnetic energy charged in the first inductor is discharged via the freewheel diode to make a decreased current successively flow in the capacitor. When the decreased current becomes zero, the FET is turned on again. This operation is repeated.
When the charged voltage of the capacitor becomes not less than the forward voltage of the LED circuit, current flows in the LED circuit and an LED of the LED circuit is lit.
Since the LED lighting device including a non-insulated step-down chopper has a relatively simple circuit constitution, capable of being downsized and high circuit efficiency and a desired low voltage can easily be obtained, it is suitably mounted on a bulb type LED of which a source is a commercial AC source and which includes an LED having a low load voltage. The bulb type LED has recently gained attention as a light source realizing energy-savings and substituting for a conventional incandescent lamp.
Additionally, it is known that current feedback is constituted in a manner that output current of the non-insulated step-down chopper undergoes voltage conversion by a resistor and is input in a control terminal of a control circuit via a diode.
As an LED bulb, a bulb including a smaller cap, for example, an E17 type cap is adopted in addition to a bulb corresponding to an incandescent bulb which is commercially available as a general illumination unit and includes an E26 type cap, and the LED bulb is required to be further downsized.
In such an LED lighting device using the non-insulated step-down chopper, it is effective to further downsize the non-insulated step-down chopper in order to respond to a request for further downsizing of the bulb type LED. As a unit for realizing the downsizing, applying integration technology mainly relating to a semiconductor device is considered.
On the other hand, since various voltage values are adopted for commercial AC sources in various countries, a bulb type LED compatible with the voltage value used in each country can be manufactured at a relatively low price so long as the LED lighting device can be constituted so as to be compatible with various voltage values by minimum design change.
Additionally, it is preferable for downsizing of the inductor to operate the non-insulated step-down chopper at high frequency.
A problem to be solved by the present invention is to provide an LED lighting device which is further downsized by integrating the non-insulated step-down chopper, easily compatible with various values of source voltage and excellent in control responsiveness in high frequency operation, and an illumination apparatus including the LED lighting device.